Telephone-exchange system.



C. L. GOODRUM.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED AUG-23,1915.

Patented Feb. 13, 1917.

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CHARLES L. GOODRUM, OF NEW YORK, N. Y., ASSIGNOR, BY MESNE ASSIGNMENTS, T0 WESTERN ELECTRIC COMPANY, INCORPORATED, A CORPORATION 03' NEW YORK.

Specification of Letters Eatent.

Application filed August 23, 1915.

To all whom itmay concern:

Be it known that I, CHARLES LANE Goon- RUM, a citizen of the United States residin at New York, in the county of New Yorr and State of New York, have invented certain new and useful Improvements in Telephone-Exchange Systems, of which the following is a full, clear, concise, and exact de scription.

This invention relates to telephone exchange systems, and more particularly to circuit arrangements for selector switches employed in automatic or semi-automatic telephone exchanges.

It is the object of this invention to provide a new and useful circuit arrangement for a final selector or connector switch.

According to this invention, upon the completion of the connection, the called line is supplied with current through the winding of a relay used also for the testing of the desired line. Thus the test relay controlling the operation of the selector switch serves a double purpose,,the necessity of providing special resistances through which current may be supplied to the called line being done away with.

The drawings represent diagrammatically an automatic telephone exchange system, and more in detail the circuits of a final selector or connector switch, only so much being shown of the apparatus and the circuits as is necessary for a clear understanding of the invention.

The subscriber at substation 1 desiring to establish a connection with a substation 2, removes his receiver from the switchhook and operates a calling device 3 for extending his line by means of switching mechanism comprising a selector switch 4 to an incoming line or trunk leading to a selector switch 5. A circuit is closed from grounded battery through the left-hand winding of a line relay 6, the calling incoming line circuit and the right-hand winding of relay 6, to ground. Relay 6 by attracting its armature closes an energizing circuit for a slow-acting relay 7.

The subscriber at substation 1 proceeds now to send out the tens and units impulses for controlling the setting of the final selector or connector. By operating the calling Patentedlueb. 13, 191?,

Serial No. 46,891.

armature of relay 6, to ground. A further circuit is closed from ground through the armature and back contact of relay 6, the

right-hand armature and front contact of relay 7, and the winding of a slow-acting relay 11, to grounded battery.

In response to each de'energization of relay 6, magnet 8 receives an impulse and causes the stepping of the connnector brushes in a rotary direction to select a group of outgoing lines in which the line leading to the called substation 2 is located. Relays 7 and 11 being slow to release, remain energized during the vibration of the armature of relay 6. Upon the energization of relay 11, a circuit is closed from grounded battery, through the winding of slow-acting escapement magnet 12, conductor 13, the righthand armature and front contact of relay 11, the left-hand armature and front contact of relay 7 conductor 14:, and the armature and back contact of a slow-acting ringing relay 15, to ground. Escapement magnet 12 becomes energized and is maintained actuated during the sending out of a series of impulses.

After the tens impulses are sent out, a longer interruption is produced in the incoming line circuit and relay 6 remains de energized for a sufiicient period to permit the deiinergization of slow-acting relay 11,

whereupon the circuit of magnet 12 is opened. This magnet becomes denergized and allows the side-switch wipers to escape into position 2. In this position of the sideswitch, primary magnet 8 is disconnected and the secondary magnet 16 is connected in circuit.

The subscriber at substation 1 proceeds now to send out the units impulses. Relay 11 and magnet 12 become energized in the same manner as above described, but the imto the called substation 2.

pulsesrepeated by relay 6 are transmitted to a secondary magnet 16 instead of the primary magnet 8. Under the control of magnet 16 the brushes of connector 5 are stepped in a vertical direction onto the line leading After the sending out of the units impulses, relay 6 retains its armature attracted and opens the circuit of relay 11. Relay 11 slowly releases and opens the circuit of magnet 12.

As well known, the busy or idle condition of the substation lines is designated by certain electrical conditions existing on the multiple test terminals thereof, Let us suppose that in the presentcase the busy condition of substation 2 is indicated by a ground connection to test terminal 20 and the multiples thereof, and the idle condition of this substation by a grounded battery connection to this terminal.

As soon as the test brush 21 reaches terminal 20 individual to the called station, and if this station is not engaged in conversation as a calling or called subscriber, a circuit is established from grounded battery through terminal 20, brush 21, side-switch wiper22, conductor 23, left-hand back contact and armature of relay 11, conductor 24, contact 25 of a test relay 26, side-switch wiper 27, and the left-hand winding of relay 26, to battery. This circuit is closed after the opening of the circuit of the slow-acting escapement magnet 12. The called line being idle, relay 26 does not become energized and therefore the circuit of magnet 12 is opened upon the retraction of the armature of relay 11. Magnet 12 becomes deenergized and moves the side-switch wipers into position 3. I

In position 3 of the side-switch, a circuit is closed from grounded battery through the winding of magnet 12, conductor 13, sideswitch wiper 30, conductor 31, the left-hand front contact and armature of relay 7, conductor 14, the armature and backcontact of relay 15, to ground. Upon the energization of magnet 12 a ringing circuit is established from ground through a ringing current generator 32, the front contact and armature of magnet 12, side-switch wiper 33, the called substation loop and side-switch wiper 34, to ground, for signaling the called station. As soon as the called subscriber at station 2 removes his receiver from the switchhook, relay 15 becomes energized and opens the circuit of escapement magnet 12, whereupon the side-switch wipers are moved into position 4. Relay 15 becomes deenergized and the ringing current is disconnected from the called line. A circuit is also closed from ground through side-switch wiper 35, the right-hand winding of relay 26, the called substation loop, side-switch Wipers 33 and 27- and the left-hand winding of relay 26, to

grounded battery for energizing this relay. The called substation is supplied with cur rent through the windings of test relay 26,

' and the calling station through the windings ofrelays 6 and 26. Relay 7 becomes denergized and a circuit is closed from grounded battery, through the secondary windingof an induction coil 40, the winding of a restoring magnet 41, the right-hand armature and back contact of relay 26, an cit-normal contact 42 of connector 5, conductor 24, the left-hand back contact and armature of relay 7, conductor 14, the left-hand armature and back contact of relay 15, to ground. This circuit remains closed as long as contact 42 is closed, 2'. 6., until connector 5 returns to its normal position, magnet 41 cansing the restoration of the side-switch and connector 5 to normal.

If the called line is busy, 2'. e. if ground is connected to terminal 20, the above traced circuit of relay 26 results in the energization of this relay. Relay 26 closes a circuit from ground through the back contact and armature of relay 15, conductor 14, the left-hand armature and front contact of relay 7, conductor 31, the left-hand armature and front contact of relay 26, conductor 50, side-switch wiper 30 and the winding of escape magnet 12, to grounded battery. The escape magnet is maintained energized after the deenergization of relay 11 and the sideswitch wipers remain in position 2. A circuit is closed from grounded battery through the secondary winding of inductance coil 40 the winding of magnet 41, the right-hand armature and front contact of relay 26, sideswitch wiper 35, the right-hand winding of relay 26 and the calling substation loop. A characteristic signal is sent to the calling substation from an alternating current source 51 for indicating the busy condition of the desired line.

The calling subscriber restores his re ceiver to the switchhook opening thereby the incoming lino circuit. Relays 6 and 7 and magnet 12 become deenergized, and the side-switch wipers are moved into position 3. In this position, relay 26 is deprived of current and a circuit is closed from grounded battery through the primary Winding of induction coil 40, the winding of magnet 41, the right-hand armature and back contact of relay 26, off-normal contact 42, the lefthand armature and back contact of relay 7,

conductor 14:, and the armature and back contact of relay 15, to ground. Magnet 41 becomes energized and causes the restoration of the side-switch wipers and the connector 5.

Selector 4 and the other apparatus employed in the building up of the connection are restored to normal in any well-known manner.

\Vhat'is claimed is:

1. In a telephone exchange system, a plurality of lines, a selector switch for extending a calling to a called line, a relay associated with said selector for testing the busy or idle condition of the called line. and means for supplying current for talking purposes to the called line through a winding of said relay.

2. In a telephone exchange system, a plurality of lines, a selector switch for extending a calling to a called line, a double wound relay for testing the busy or idle condition of a. selected called line, and means for supplying current for talking purposes to the called line through the windings of said relay.

3. In a telephone exchange system, a plurality of lines, a selector switch for establishing a connection between a calling and a called line, a relay for testing the busy or idle condition of the called line, said relay controlling the completion of the connection, and means for supplying current for talking purposes to the called line through the winding of said relay if said line has been found idle.

4. In a telephone exchange system, a plurality of lines, a selector switch for extending a calling to a called line, a double wound relay for testing the busy or idle condition of the called line, a restoring magnet for said selector switch. means for sending a characteristic signal to the calling line through a winding of said relay if the called line is busy, the operation of said means and said restoring magnet being controlled by said relay.

5. In a telephone exchange system, a plurality of lines, a selector switch for extending a calling to a called line, a relay adapted to be actuated if the called line is found busy, at restoring magnet for said selector switch, means ope 'ative upon the actuation of said relay for sending a characteristic signal to the calling line, and means operative upon the reaction of said relay for closing an actuating circuit for said restoring magnet.

(3. In a telephone exchange system, a plurality of lines, a selector switch for extending a calling to a called line, a relay adapted to be actuated if the called line is found busy, a restoring magnetfor said selector switch, an apparatus for producing a characteristic signal, means operative upon the actuation of said relay for connecting said apparatus through the winding of said restoring magnet to the calling line, means controlled by the calling line for causing the reaction of said relay, and means operative thereupon for disconnecting said signaling apparatus and establishing an actuating circuit for said restoring magnet.

7. In a telephone exchange system, a plurality of lines, a selector switch for establishing a connection between a calling and a called line, a double wound relay for testing the busy or idle condition of the called line, means for sending a characteristic signal to the calling line through one of the windings of said relay if the called line is busy, and means for supplying current for talking purposes to the called line through. the other winding of said relay.

In Witness whereof, I hereunto subscribe my name this 20th day of August A. D., 1915.

CHARLES L. GOODRUM. 

